Because she didn't write it.
Seriously, what's the deal with that phrase? "Not your mama's..." I hope it goes away soon.
I have to admit that I thought it was cute at first, in some product names. "Not your mama's shampoo." Or something like that. It was fun.
And then my editor pointed out that it's rude. You should want something to be your mama's or grandma's. Mamas and grandmas deserve respect.
But really, I want to say today that you won't be just like your mother, but (in most cases) you will be lucky if you are. Motherhood is the most ancient of traditions, and the most personal. Unlike your childhood, you can make your motherhood whatever you want it to be. Wanna be a flower mama who wears long hair and maxi dresses? Do it. Wanna be a corporate mama in Hilary Clinton-esque power suits? I dare you. Wanna be both? You got it. Wear all the hats you want, all the outfits or uniforms that suit you, because you do a million different jobs. You can be it all. You can have it all.
Except for sleep. It's a waste of energy to even think about that.